Pull to refresh leaves a style 'transform: translate(0);' in the div element with class="scroll-content". This prevents any child elements that have a 'position: fixed;' from remaining in a fixed position.
I noticed this behavior when creating a new page for an activity where I used a standard FAB (fixed action button). The button works fine until a PTR, when it then scrolls with the page.
PTR adds the transform style on every page I have looked at, so this could affect anyone else adding a fixed position element on almost any page.
The fix would be to just remove the transform style from the DOM at the end of the PTR.